Bite device used with a panorama x-ray device

ABSTRACT

A bite device for the correct positioning of a patient when a panoramic X-ray is taken, comprising a holder part which can be placed in a fixed direction in relation to the X-ray device, a plate which can pivot against the holder and which is provided with a bite part into which a patient bites, and means for detecting the pivoting angle A between the plate and the holder part.

BACKGROUND OF THE INVENTION

The invention relates to a system for correct positioning of a patientwhen the latter is X-rayed with a medical panoramic X-ray device.

PRIOR ART

When recording a panoramic X-ray image, the tomography zone ideally runsthrough the alveolar ridge of the patient. In order to achieve a highdegree of recording quality, it is necessary to bring these twoelements, tomography zone and alveolar ridge, into the best possiblespatial relationship. In the panoramic X-ray device, the tomography zonecan be adjusted to the individual shape and position of the jaw of apatient within certain limits. The condition is, however, that these areknown to the operator. In particular, knowledge of the followingfeatures is significant:

-   -   the spatial orientation of the edge-to-edge occlusal plane (bite        plane) relative to a reference point on the panoramic X-ray        device; and    -   the individual anatomic characteristics of the jaw: its size,        shape, anomalies and the like.

Traditionally, the patient's head is fixed in position relative to thedevice for taking a panoramic radiograph by means of a patient's headpositioner comprising a forehead pad and/or ear pads, a bite block, anasion, or a chin pad. The necessary alignment of the head is usuallyachieved with the aid of optical lines projected onto the patient's headand depicting the Frankfurt horizontal and median planes. The Frankfurthorizontal plane runs through the right and left porion, the highestpoint of the meatus acusticus externus, and the orbital, whichrepresents the lowest point of the osseous edge of the orbita. Theprojected median plane runs as a sagittal plane from the crown of thehead through the center of the nose to the chin. It assists symmetricalpositioning of the head.

The position of the occlusal plane is not directly registered but onlyindirectly by way of the Frankfurt horizontal plane. To this end, theFrankfurt horizontal plane projected onto the patient's head by thepanoramic X-ray device and the incisal teeth in the edge-to-edge biteare used to derive the position of the occlusal plane. The correlationbetween the occlusal plane and the Frankfurt horizontal plane isgenerally acknowledged from an anatomical standpoint, but positioningerrors relative to the Frankfurt horizontal plane of the patient cannotbe excluded.

In order to determine the individual size of the patient's jaw, afrontal diameter measurement may be carried out, if necessary.Derivation of the jaw size is not, however, sufficiently reliable.

Neither has any reliable system been as yet developed for determiningthe shape of the alveolar arch or any anomalies of the jaw.

Present-day panoramic X-ray devices, therefore, offer only a fewmodification options, since the operator could not in any case make useof such adjustment options due to insufficient knowledge of theindividual form of a patient's jaw.

This forms the basis of the invention. It is an object of the invention,as characterized in the claims, to provide a system for correctpositioning of a patient for image recording using a medical panoramicX-ray device, which allows for simple and stable measurement and/oradjustment of the inclination of the occlusal plane of a patient.

DESCRIPTION OF THE INVENTION

This object is achieved, according to the invention, by the bite devicedefined in claim 1. Advantageous embodiments of the invention aresubject matter of the sub-claims.

The invention improves on the prior art in that a bite device includes aholding member held in a directionally fixed position relative to theX-ray device, and a plate which is pivoted relative to the holdingmember and which has a bite piece on which the patient bites. The bitedevice also includes means for measuring the angle of deflection αbetween the plate and the holding member, which means for measuring theangle of deflection α are located in a zone of the bite device which isfree from radiation during X-ray imaging. The zone involving X-rayirradiation can therefore be kept substantially free from metal.

The invention is thus based on the idea of measuring the position of theocclusal plane of the patient relative to the device by determining theposition of a plate disposed in the occlusal plane. For this purpose,the angle is measured between the plate and a holding member, which canbe positioned relative to the X-ray device in fixed alignment. From thisangle a signal can be derived which indicates the degree of inclinationof the occlusal plane.

It is advantageous for the means for measuring the angle of deflection ato contain one or more sensors located in the holding member. Forexample, the sensors might be in the form of a photoelectric sensorlocated in the holding member and adapted to register the position of anopening that is moved upwardly and downwardly in accordance with thepivotal motion of the plate.

The bite device of the invention can conveniently include means fordisplaying the angular position of the pivoted plate.

In a preferred development of the bite device, there are furtherprovided driving means for vertical adjustment of the holding member andthus for pivoting the plate into a predetermined angular position. Thismakes it possible to adapt to the patient's body size, and the patientcan be constrained to adjust the inclination of his head to theinclination of the plate, so that a desired angular position of thepatient's occlusal plane relative to the X-ray device will be achieved.

It is advantageous for the plate-swinging means to move the plate to thepredetermined angular position automatically and to stop when thepredetermined angular position has been reached.

Alternatively or additionally, provision may be made for said means toindicate that the predetermined angular position of the plate has beenreached by emitting optical and/or acoustic signals.

In a preferred embodiment of the bite device of the invention, thepivoted plate is connected to a rail within the holding member, whichrail can be moved upwardly and down-wardly and has an opening forindicating the position of the rail in the holding member.

The bite piece of the bite device is preferably equipped with areplaceable protective sheath for hygienic reasons.

Alternatively, the bite piece can be in the form of a replaceable bitepiece. The bite piece is preferably composed of a soft material,particularly a substantially radiolucent material. It has proved to beparticularly suitable to fabricate the bite piece from closed-cellethylene foam.

The bite piece preferably occupies an angular range β of the mandibulararch, which is between 20° and 40°, particularly 30°. This substantiallyprevents any sideways tipping or tilting of the patient's head.

In an advantageous embodiment, the bite piece has on its upper surfaceand on its undersurface a bite groove to accommodate part of the dentalarch of the patient's upper and lower jaw respectively.

The bite piece is preferably a unitary piece foldable about a foldingedge. It preferably has on opposite sides a wedge-shaped projection anda complementary depression for the accommodation of said projection, toenable the bite piece to be removably attached to the pivoted plate.

Further advantageous embodiments, features, and details of the inventionare given in the dependent claims, the description of embodiments, andthe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail with reference to anembodiment and the drawings. Only those elements are shown which aresignificant for comprehension of the invention.

In the drawings:

FIG. 1 is a diagrammatic illustration of a panoramic X-ray system;

FIG. 2 is a diagrammatic representation of the system for aligning thetomography zone of the X-ray device to the alveolar arch of a patient;

FIG. 3 shows a perspective view of a bite device according to oneembodiment of the invention, shown diagrammatically;

FIG. 4 is a cross-section through the bite device of FIG. 3;

FIG. 5 shows perspective views of an bite piece for a bite deviceaccording to one embodiment of the invention, shown (unfolded)diagonally from below in FIG. 5( a) and diagonally from above in FIG. 5(b);

FIG. 6 is a cross-section through the bite piece of FIG. 5, taken alongline VI-VI; and

FIG. 7 shows the bite piece of FIG. 5 in the folded position, asattached to the bite device of FIG. 3.

DESCRIPTION OF EMBODIMENTS

FIG. 1 is a diagrammatic representation of a panoramic X-ray system 10,in which a rotary unit 12 carries a radiation source 14 equipped with ashutter 16, and a diametrically opposed detector camera 18 equipped witha shutter 20. The beam of X-rays 22 emitted from the radiation source 14transilluminates the jaw region of the head 24 of a patient and producesan image signal in detector camera 18. This is directed to a controlunit 26 for evaluation and display in the usual manner.

Rotary unit 12 is pivotally or hingedly mounted on an arm 11 which ismounted on a column 13 for vertical adjustable thereon. A drive 15 isprovided to perform the vertical adjustment. In this way, the positionof X-ray emitter 14 and detector camera 18 can be adjusted to thestature of the patient. It is essential, for obtaining a faultless,high-quality panoramic radiograph, for the tomography zone 30 (FIG. 2)to be in line with the alveolar arch 32 of the patient. FIG. 2 depictsperfect spatial alignment of these two elements, this ensuring theproduction of a qualitatively good image. Insufficient alignment cannecessitate a repeat radiograph, resulting in increased X-irradiation ofthe patient and additional expense in terms of material and time.

FIG. 3 is a perspective view of a bite device referenced as 40,according to one embodiment of the invention, shown diagrammatically,and FIG. 4 is a cross-section through the bite device 40 of FIG. 3. Bitedevice 40 has a holder 42 which is hinged to a thin plate 46 by means ofa pivot 44. The thin plate 46 is adjoined, at its end remote from pivot44, by an imaging zone 48 parallel to said thin plate.

The imaging zone 48 has an opening 62 by means of which, in a manner tobe described in more detail below, a replaceable bite piece 50 can bequickly and easily attached to the thin plate. On its upper surface andon its undersurface, bite piece 50 has occlusal grooves 64 and 66respectively, which accommodate the dental arches of the patient's upperand lower jaw respectively. This arrangement ensures that the thin plate46 runs parallel to the occlusal plane of the patient when he bites onthe bite piece 50 for taking the radiograph.

The angle of deflection a of thin plate 46 is measured using a rail 54capable of being moved upwardly and down-wardly and connected to thinplate 46 in a region 56, and adapted to extend vertically down theinside 52 of the holding member 42. In its lower section, rail 54 isprovided with a hole 58. The vertical position of hole 58 is detected bytwo photodetectors indicated by arrows 60. The angle of deflection ofplate 46 can be deduced from said vertical position. By transferring theinclination of plate 46 to the movable rail, measurement of the angle ofdeflection a is carried out in a region of holder 42 which is far belowplate 46 and is free from radiation. The X-irradiated region can thus bekept substantially free from metal.

The bite device cooperates with a driving system 15 shown in FIG. 1 suchthat rail 54 moves upwardly or downwardly and the thin plate 46 can thusbe brought into any desired position. The deflection of thin plate 46accompanying such vertical adjustment makes it possible to gently guidethe patient's head until it assumes the correct degree of inclinationfor the panoramic radiograph.

Vertical adjustment of plate 46 can be performed interactively by theoperator. For example, the operator can press an adjustment button untilthe desired degree of inclination is attained. When a previously definedangular position, for example α=105°, which corresponds to an anglebetween plate 46 and the horizontal of 15°, is attained, this can beindicated by means of optical and/or acoustic signals.

Alternatively, the drive can automatically move plate 46 into thepredetermined angular position and stop when the desired position isreached. Additionally, the angular position of the plate can bedisplayed for checking by the operator.

The bite piece 50 shown in FIGS. 3 and 4 will now be described in moredetail with reference to FIGS. 5 through 7. FIG. 5 shows, in FIG. 5( a)and FIG. 5( b), a per-spective view of the unfolded insert, showndiagonally from below in FIG. 5( a) and diagonally from above in FIG. 5(b). FIG. 6 shows a cross-section through the bite piece taken along lineVI-VI of FIG. 5( b), and FIG. 7 represents the bite piece in the foldedposition, as attached to the bite device of FIG. 3.

In the present embodiment, bite piece 50 is fabricated as a single pieceof closed-cell ethylene foam, a soft and substantially radiolucentmaterial. On its upper surface, bite piece 50 has occlusal grooves 64and 66 adapted to accommodate part of the dental arch of the upper andlower jaws of the patient. Bite piece 50 can be folded along a centralfolding edge 70, defined by notches 72 on the undersurface and a centralgroove 74 on the upper surface of the insert.

On its underside, bite piece 50 has a wedge-like tapered projection 76which, when the insert is folded, slides into a complementary depression78 located on the opposite side of the insert, this making for a stablebut easily releasable connection. The flat imaging zone 48 of the bitedevice contains an opening 62 (FIG. 4) through which the projection 76projects when the bite insert is attached, so that insert 50 is firmlyattached to the thin plate 46 of the bite device once it has been foldedtogether. After use, however, the insert can be unfolded with no greateffort and thrown away for hygienic reasons.

The insert shown in the embodiment illustrated in FIGS. 5 through 7, hasa width of 40 mm, occupies an angular region β of the dental arch ofabout 30°. In order to accommodate for different jaw sizes of patients,bite pieces are also fabricated and used in other widths. The differentwidths can be easily distinguished by the user on the basis of differentcolor markings or other labels. With this kind of bite piece, theposition of the patient can be fixed with great accuracy but withoutdiscomfort for the patient.

LIST OF REFERENCE NUMERALS OR CHARACTERS

-   10 radiographic system-   12 unit-   14 source of radiation-   15 driving system-   16 shutter-   18 detector camera-   20 shutter-   22 beam of X-rays-   24 head-   26 evaluation unit-   30 tomography zone-   32 alveolar arch-   40 occlusal device-   42 holder-   44 pivot-   46 plate-   48 imaging zone-   50 bite piece-   52 interior of holding member 42-   54 rail-   56 region-   58 hole-   60 arrows-   62 opening-   64 occlusal groove-   66 occlusal groove-   70 folding edge-   72 notches-   74 central groove-   76 projection-   78 depression

1-16. (canceled)
 17. A bite device for correct positioning of a patientfor taking a radiograph with a panoramic X-ray device, comprising: aholding member; a plate pivotally attached to said holding member, saidplate including a bite piece on which the patient bites; means fordetecting an angle of deflection a between said plate and said holdingmember, and driving means for vertically adjusting said holding memberand said plate.
 18. A bite device as defined in claim 17, whereindriving means are provided for vertical adjustment of said holdingmember and thus to pivot said plate.
 19. A bite device as defined inclaim 17, wherein said driving means move said plate automatically intoa predefined angular position and stop when said predefined angularposition is attained.